Electrodiagnostic Testing

Number: 0502

Table Of Contents

Policy

Scope of Policy

This Clinical Policy Bulletin addresses electrodiagnostic testing (EDX), which encompasses the following procedures for diagnosis and follow-up (or evaluation) of neuromuscular disorders:

• Nerve conduction studies (NCS)
• Needle and single fiber electromyography (EMG)
• Neuromuscular junction testing (e.g., repetitive nerve stimulation [RNS] studies)
• Late responses (H-reflex and F-wave studies)
• Blink reflex studies.

For testing performed in conjunction with primary intraoperative neuromonitoring, see CPB 0697 - Intraoperative Neurophysiological Monitoring. 

For diagnostic testing of central nervous system (CNS) disorders that include somatosensory evoked potentials (SEPs, SSEPs), central motor evoked potentials (MEPs), and visual evoked potential (VEPs), see CPB 0181 - Evoked Potential Studies.

1. Medical Necessity

   Aetna considers the following electrodiagnostic (EDX) tests to be medically necessary when criteria are met:

   1. Nerve conduction studies (includes sensorimotor nerve conduction velocities [NCV] and late responses [H-reflex and F-wave studies]):

      1. Member has any of the following indications and, when applicable, disease-specific criteriaFootnote1* are met:

         1. Diagnosis and prognosis of traumatic nerve lesions (e.g., spinal cord injury, trauma to nerves); or
         2. Diagnosis and monitoring of neuromuscular junction disorders (e.g., myasthenia gravis, myasthenic syndrome) using repetitive nerve stimulation; or
         3. Diagnosis of muscle disorders (e.g., muscular dystrophy, myositis, myopathy); or
         4. Diagnosis or confirmation of suspected generalized neuropathies (including uremic, metabolic or immune) (e.g., Guillain-Barré Syndrome, post-polio syndrome); or
         5. Differential diagnosis of physical examination findings of sensory loss, weakness and/or muscle atrophy with no known etiology (e.g., amyotrophic lateral sclerosis, diabetes, hypothyroidism, lupus, rheumatoid arthritis, etc.); or
         6. Differential diagnosis of symptom-based complaints (e.g., pain in limb or joint, weakness, fatigue, cramps, twitching (fasciculations), disturbance in skin sensation or paresthesias [numbness or tingling]) provided the clinical assessment supports the need for a study; or
         7. Localization of focal neuropathies or compressive lesions (e.g., Bell's palsy of the facial nerve, carpal tunnel syndromeFootnote1*, cubital tunnel syndromeFootnote1*, tarsal tunnel syndrome, nerve root compression, neuritis, motor neuropathy, mononeuropathy, radiculopathyFootnote1*, plexopathy); or
         8. Peripheral neuropathy (e.g., distal symmetric polyneuropathy) - unexplained peripheral neuropathy with pain of a neuropathic pattern, and with demonstrated motor loss or sensory loss, all of unknown etiology; and

      2. Footnote1* The following disease-specific criteria are met, where applicable:

         1. Carpal tunnel syndrome

            For evaluation of individuals suspected of having carpal tunnel syndrome:

            1. Sensory conduction studies across the wrist with a conduction distance of 13-14 cm of the median nerve, and if the results are abnormal, of one other sensory nerve in the symptomatic limb; and
            2. If the initial median sensory nerve conduction study across the wrist has a conduction distance greater than 8 cm, and the results are within normal limits (see Appendix), one of the following additional studies will be considered medically necessary:
               
               
               1. Comparison of median sensory conduction across the wrist with radial or ulnar sensory conduction across the wrist in the same limb; or
               2. Comparison of the median sensory or mixed nerve conduction with ulnar sensory nerve conduction across the wrist over a short (7 to 8 cm) conduction distance; or
               3. Comparison of median nerve conduction through the carpal tunnel to proximal or distal segments of the median nerve in the same limb; and

            3. Motor conduction studies of the median nerve recording from the thenar muscle and of one other nerve in the symptomatic limb to include measurement of distal latency; or

         2. Cervical, thoracic or lumbar radiculopathy

            For evaluation of cervical, thoracic or lumbar radiculopathy when all of the following criteria are met:

            1. Persistent or progressive symptoms; and
            2. Failed non-surgical medical management with at least 6 weeks of formal physical therapy in the past year (in-person as opposed to home or virtual physical therapy). Physical therapy needs to be confirmed either by the actual PT notes, or by documentation in the member claims history; and
            3. Unexplained by imaging studies (e.g., magnetic resonance imaging [MRI], myelogram, etc.); or

         3. Cubital tunnel syndrome criteria

            For individuals with symptoms and positive physical signs of distribution region of ulnar nerve (e.g., pain and numbness of the forearm and finger, weakness of hands and muscles atrophy). Note: If ulnar sensory or motor NCS are abnormal, further NCSs should be performed to exclude a diffuse process; or 

         4. Distal symmetric polyneuropathy (DSP)

            For persons with suspected distal symmetric polyneuropathy (DSP) when any of the criteria are met: 

            1. The presentation does not indicate an etiology (e.g., history and physical, and standard neuropathy blood tests to screen for common and treatable causes such as diabetes [glucose, HbA1c], vitamin deficiencies [B12], and autoimmune conditions [serum protein electrophoresis; SPEP]); or
            2. Symptoms and/or physical findings are moderate to severe; or
            3. An atypical presentation (i.e., motor, asymmetric or proximal deficits); or
            4. Rapid progression of symptoms or signs; or
            5. Discrepancy between signs and symptoms; or
            6. History of exposure to medications (e.g., taxanes, lithium) or toxins known to cause neuropathy; or
            7. Familial history of hereditary neuropathy affecting first degree family members; or
            8. Underlying severity and duration of etiology; and/or
            9. Overlapping symptoms or signs to suspect another diagnosis (i.e., radiculopathy);

         Aetna considers NCS experimental, investigational, or unproven for screening neuropathy when symptoms and physical findings are mild, primarily sensory and with a known cause. 

         Aetna considers EDX testing experimental, investigational, or unproven when these disease-specific criteria are not met.

      3. Unless an approvable exception is documented, NCS cannot be approved without an approvable EMG request.

         NCS studies are considered experimental, investigational, or unproven when these criteria are not met.

   2. Needle electromyography (EMG)

      Aetna considers needle EMG performed concurrently with nerve conduction studies (NCS) to be medically necessary when the above NCS criteria are met (includes disease-specific criteria when applicable):

      1. Standard needle (monopolar or concentric) EMG

         1. The requirement for needle EMG with NCS may be waived for persons with coagulation disorders or on anti-coagulant therapy with warfarin (Coumadin), direct thrombin inhibitors (e.g., dabigatran [Pradaxa], desirudin [Iprivask]), or heparins that cannot be interrupted;
         2. Unless an approvable exception is documented for EMG (as per above), NCS is considered not medically necessary. For EMG requests without performance of NCS, refer to Appendix D; or 
            

      2. Single fiber EMG

         For the evaluation of neuromuscular disorders (i.e., Myasthenia Gravis (MG) and Lambert-Eaton Myasthenic Syndrome (LEMS). Reporting should include neuromuscular jitter and muscle fiber density (FD).

         Needle EMG studies are considered experimental, investigational, or unproven when these criteria are not met.

   3. Neuromuscular Junction Testing

      To diagnose persons with fatigable weakness who are being evaluated for possible disease of the neuromuscular junction: Note: Reporting should include the rate of repetition of stimulations, and any significant incremental or decremental response.

      1. Autoimmune neuromyotonia; or
      2. Botulisms; or
      3. Congenital myasthenic syndrome; or
      4. Lambert-Eaton myasthenic syndrome; or
      5. Motor neuropathy (e.g., amyotrophic lateral sclerosis); or
      6. Myasthenia gravis; or
      7. Myopathy; or
      8. Symptoms of diplopia, dysphagia, or fatigable weakness that increases with repetitive activity.

      Neuromuscular junction testing is considered experimental, investigational, or unproven for all other indications.

   4. Blink Reflexes

      To evaluate disease involving the 5th or 7th cranial nerves or brainstem. Note: Recordings should be made bilaterally with both ipsilateral and contralateral stimulation.

      Blink reflexes are considered experimental, investigational, or unproven for all other indications.

   5. Documentation requirements for EDX testing [excludes Blink reflexes]

      1. Documentation should include relevant history and physical examination that establish the working diagnosis and need for EDX testing.
      2. The NCS and EMG are performed by a physician trained in electrodiagnostic medicine, or by resident/fellow with direct supervision by an EDX-trained physician, and includes real-time interpretation conducted by the EDX-trained physician. Only physicians should perform any portion of the examination which requires needle insertion (EMG). Technologists are able to perform NCS only (AANEM, 2025).
      3. NCS is performed, reported, and interpreted with the associated needle EMG on-site and in real time in accordance with the American Medical Association Current Procedural Terminology (CPT) code requirements for these procedures.
      4. A full EDX report must be submitted. This report should include all EDX tests performed, including data summary tables (see Appendix B). Forwarding the NCS waveforms is encouraged. 
      5. Additional documentation justifying the need for studies beyond the generally accepted amount for the member’s condition(s), as illustrated in the Maximum Number of Studies Table (see below).

   6. Frequency of Testing 

      The following table includes the American Association of Neuromuscular & Electrodiagnostic Medicine's (formerly known as American Association of Electrodiagnostic Medicine) recommendation for the maximum number of EDX studies considered necessary for certain diagnostic categories in 90% of cases. The CPT descriptor language for CPT codes 95907-95913 describes one or more NCSs. For the purposes of coding, a single conduction study is defined as a sensory conduction test, a motor conduction test with or without an F wave test, or an H-reflex test. Requests are subject to case review when there is deviation from established norms for quantity and variety of procedures. This section excludes Blink reflexes. 

      Following the member's history and examination, the physician conducting the EDX testing formulates a working diagnosis that may adjust the initial referral diagnosis as the study progresses. Multiple tests may be required to address both the referral and working diagnoses in order to reach an accurate final diagnosis. When multiple diagnoses are submitted, coverage is determined based on the diagnosis allowing the greatest number of studies in the table below, as the required diagnostic studies typically overlap and, except in rare circumstances, can be applied across multiple conditions (see documentation requirements above). Additionally, it is important to note that EDX testing may not always provide a definitive etiologic diagnosis.

      Table: Maximum Number of Studies - EDX Medicine Listing of Sensory, Motor, and Mixed Nerves

      Indication	Limbs Studied by Needle EMG (95860-95864, 95867-95870, 95885-95887)	Nerve Conduction Studies (Total nerve studied, 95907-95913)		Neuromuscular Junction Testing (Repetitive Stimulation)
      	Number of Services (Tests)
      Carpal tunnel (unilateral)	1	7		--
      Carpal tunnel (bilateral)	2	10		--
      Radiculopathy	2	7		--
      Mononeuropathy	1	8		--
      Polyneuropathy/Mononeuropathy Multiplex	3	10		--
      Myopathy	2	4		2
      Motor Neuropathy (e.g., ALS)	4	6		2
      Plexopathy	2	12		--
      Neuromuscular junction	2	4		3
      Tarsal tunnel syndrome (unilateral)	1	8		--
      Tarsal tunnel syndrome (bilateral)	2	11		--
      Weakness, fatigue, cramps, or twitching (focal)	2	7		2
      Weakness, fatigue, cramps, or twitching (general)	4	8		2
      Pain, numbness, or tingling (unilateral)	1	9		--
      Pain, numbness, or tingling (bilateral)	2	12		--

      Source: AANEM, 2025

      To qualify as a single NCS, see Appendix J, "Electrodiagnostic Medicine Listing of Sensory, Motor, and Mixed Nerves," within the official CPT codebook published by the American Medical Association (AMA). Each line on the list of nerves refers to a different nerve and should be billed as an individual unit. It is inappropriate to bill more than one unit for “inching” or studying the same nerve by moving the stimulating electrode closer to the recording electrode, (i.e., ulnar nerve at the elbow). It should be noted that most nerves have a contralateral counterpart; bilateral testing is often necessary for comparison purposes and the nerve on each side may be billed separately.

      Frequency of EDX Testing in a Member

      Aetna considers two EDX tests per year to be medically necessary per diagnosis and when criteria have been met in Section I. Additional testing may be considered medically necessary once per year for the following conditions when medical records document the medical necessity of the additional study. The following number of tests per year per diagnosis are considered acceptable:

      1. Two tests per year:

         1. Carpal tunnel (unilateral and bilateral)
         2. Radiculopathy
         3. Mononeuropathy
         4. Polyneuropathy
         5. Myopathy 
         6. Neuromuscular Junction disorders

      2. Three tests per year:

         1. Motor neuronopathy
         2. Plexopathy

      3. Exceptions:

         The following exceptions may apply in certain cases based on physician review:
         

         1. Evaluation by more than one EDX physician (e.g., second opinion) in a given year
         2. Inconclusive diagnosis
         3. Rapidly evolving disease that initial EDX testing may not show any abnormality (e.g., early Guillain-Barre syndrome)
         4. Course of the disease is fluctuating with variable response to treatment
         5. Unexpected or change in course of the disease (e.g., failure to improve after surgery for radiculopathy)
         6. Recovery from injury (e.g., monitor recovery, prognosticate, and determine timing of surgical intervention, such as from traumatic nerve injury)
         7. New set of symptoms (e.g., evaluation for a second diagnosis the same year).

   Utilization of motor or sensory nerve conduction velocity studies at a frequency of 2 sessions per year would be considered appropriate for most conditions (e.g., carpal tunnel syndrome (unilateral or bilateral), radiculopathy, mononeuropathy, polyneuropathy, myopathy, and neuromuscular junction disorders). Nerve conduction velocity EDX testing studies performed more frequently than outlined per condition without a qualifying clinical situation twice a year may be reviewed for medical necessity.

2. Experimental, Investigational, or Unproven

   Aetna considers the following interventions experimental, investigational, or unproven because the effectiveness of these approaches has not been established:

   1. Cadwell Sierra II System
   2. Examination/NCS studies using the ADVANCE NCS/EMG System, Brevio NCS monitor, Cadwell Sierra, NC-stat DPNCheck, NC-stat monitor, Neural Scan - Axon II, VT3000, XLTEK Neuropath, and other automated devices
   3. F-wave (F-reflex) study for carpal tunnel syndrome
   4. NCS for diagnosis of organophosphorus pesticide exposure
   5. NCS for evaluation of COVID-19 associated neuromuscular disorders
   6. NCS for evaluation of Peyronie's disease
   7. NCS for screening for polyneuropathy of diabetes or end-stage renal disease
   8. NCS for the sole purpose of monitoring disease intensity or treatment effectiveness for polyneuropathy of diabetes or end-stage renal disease
   9. Phrenic nerve conduction study for evaluation of phrenic nerve function of lung transplant candidate; 
   10. The Medi-Dx 7000™ and Neural-Scan. 

3. Related Policies

   • CPB 0112 - Surface Scanning and Macro Electromyography
   • CPB 0181 - Evoked Potential Studies
   • CPB 0221 - Quantitative EEG (Brain Mapping)
   • CPB 0289 - Grid Monitoring and Intraoperative Electroencephalography
   • CPB 0357 - Quantitative Sensory Testing Methods
   • CPB 0362 - Spasticity Management
   • CPB 0485 - Autonomic Testing / Sudomotor Tests
   • CPB 0697 - Intraoperative Neurophysiological Monitoring
   • CPB 0745 - Facial Nerve Paralysis

Background

Electrodiagnostic (EDX) testing encompasses a set of physiologic assessments—primarily nerve conduction studies (NCS) and needle electromyography (EMG)—used to evaluate the integrity and function of peripheral nerves, neuromuscular junctions, and muscles. NCS measure the electrical responses of peripheral nerves to controlled stimulation, allowing quantification of nerve conduction velocity, amplitude, and latency, which differentiate axonal loss from demyelination. Needle EMG directly evaluates muscle electrical activity at rest and during voluntary contraction to identify denervation, reinnervation, or myopathic processes. Specialized components of EDX include neuromuscular junction testing (e.g., repetitive nerve stimulation or single‑fiber EMG) to detect transmission disorders such as myasthenia gravis; late responses such as the H‑reflex and F‑wave, which assess proximal nerve segments and spinal reflex pathways; and blink reflex studies, which evaluate brainstem reflex circuits and are useful for diagnosing cranial neuropathies or central lesions. Collectively, these modalities provide complementary, evidence‑based physiologic data that guide diagnosis, severity grading, and localization of neuromuscular disorders.

Nerve conduction testing, also known as nerve conduction studies (NCS) measures the speed of conduction of impulses through a nerve. The impulses that are measured are generated by placing a stimulating electrode on the skin over the nerve. Recording electrodes are placed at various distances from the stimulating electrode. The distance between electrodes and the time it takes for electrical impulses to travel between electrodes are used to determine the speed of the nerve signals. There are two parts to NCS: testing motor nerves and testing sensory nerves. NCS are performed by a physician specially trained in electrodiagnostics (EDX).

Nerve conduction velocity (NCV) studies are performed by recording and studying the electrical responses from peripheral nerves or the muscle they innervate, following electrical stimulation of the nerve. Usually, surface electrodes are employed for both stimulation and recording because of their reproducibility and ease of use. Needle electrodes may be used when there is a need to evaluate a nerve that is deep in the tissue, such as the sciatic nerve in the thigh, or the femoral nerve in an extremely obese individual.

Motor NCS are performed by stimulating two different points along a nerve and the impulse is measured by an electrode that is placed over the muscle being stimulated by that nerve. This measure is called the latency and is measured in milliseconds. The size of the response, called the amplitude, is measured in millivolts.

Sensory NCS are measured with a single stimulating electrode and a single recording electrode. This test is calculated based upon the latency and the distance between the stimulating and recording electrode.

Additional types of NCS, referred to as late responses, are H-reflex and  tests. These tests are usually performed on nerves that are more proximal (near) to the spine and, therefore, inaccessible to direct assessment using conventional techniques. These tests can be helpful when evaluating radiculopathies, plexopathies, polyneuropathies and proximal mononeuropathies.

• H-reflex study uses stimulation of a nerve and records the reflexive electrical discharge from a muscle in the limb. It also measures the conduction between the limb and spinal cord. The impulses going toward the spinal cord are known as afferent impulses and those moving away from the spinal cord are efferent impulses.
• F-wave study includes an electrical stimulation that is applied to the skin surface proximal to the distal portion of a nerve so that the impulse travels both toward the muscle fiber and back to the motor neurons of the spinal cord.

In standard nerve conduction testing, the stimulating, recording and ground electrode placement and the test design should be individualized to each patient's specific anatomy. Nerves tested should be limited to the specific nerves and conduction studies needed for the particular clinical question being investigated. The stimulating electrode is placed directly over the nerve to be tested, and stimulation parameters are adjusted to avoid stimulating other nerves or nerve branches. In most motor nerve conduction studies, and in some sensory and mixed nerve conduction studies, both proximal and distal stimulation are used. Motor nerve conduction study recordings are made from electrodes placed directly over the motor point of the specific muscle to be tested. Sensory nerve conduction study recordings are made from electrodes placed directly over the specific nerve to be tested. Waveforms should be reviewed on site in real time, and the technique (stimulus site, recording site, ground site, filter settings) should be adjusted as the test proceeds in order to minimize artifact, and to minimize the chances of unintended stimulation of adjacent nerves and the unintended recording from adjacent muscles or nerves. Reports are prepared on site by the examiner, and consist of the interpretation of test results, using established techniques to assess the amplitude, latency and configuration of waveforms elicited by stimulation at each site of each nerve tested. This includes the calculation of NCV, sometimes including specialized F-wave indices, along with comparison to normal values, summarization of clinical and electrodiagnostic data, physician interpretation, generation of a differential diagnosis, and, when appropriate, suggestions for additional testing. Electromyographic recording is usually performed during the same patient encounter in order to carry out a more in-depth evaluation of the clinical question being investigated.

Standard nerve conduction testing includes safeguards and procedures to assure proper performance and interpretation. Many of those are not used in the automated nerve testing systems. Therefore, literature about nerve conduction testing of clinical efficacy does not necessarily apply to these automated devices.

Automated devices, also known as point of care devices, perform limited nerve conduction tests and do not supplement, replace or duplicate traditional nerve conduction tests. Examples of these devices include, but may not be limited to, the ADVANCE NCS/EMG system, Brevio NCS monitor, NC–stat system and the Neural Scan - Axon II. Automated NCS testing is similar to standard NCS testing in that both involve electrical stimulation of peripheral nerves, and recording of electrical responses from the same peripheral nerve or from a muscle. Automated devices, however, have a number of differences with standard NCS tests.

With standard nerve conduction studies, the physician specialist and a registered technologist perform the testing. With automated devices, the office staff typically perform the test. Additionally, only specific nerves can be tested. Whereas standard NCS tests can stimulate and record both proximally and distally, automated devices can only stimulate and record distally. With automated devices, only one direction of conduction is available, whereas with standard NCS tests, orthodromic and antidromic conduction is available. The technique of standard NCS tests varies according to the patient's situation, whereas with automated devices, a single specific technique is pre-determined. With automated devices, electromyography (EMG) is generally not available at the point of service, although new automated devices are being developed that also have EMG capabilities. Stimulator and recording sites are placed at pre-determined anatomic locations with automated devices, whereas with standard NCS testing, stimulator and recording sites can be moved around to find optimal locations.

With standard nerve conduction tests, a trained clinician evaluates the patient’s history and examination findings, determines what electrodiagnostic testing is needed to answer the clinical question at hand. The clinician can consider the differential diagnosis as testing is conducted and change the test as needed as it proceeds to narrow the differential diagnosis. The clinician asks for further history, checks further examination findings, and integrates those with test findings in developing an interpretation. By contrast, automated NCS devices test preset nerves only.

With standard NCS testing, a trained clinician scores peaks and latencies, determining if tests are normal, adjusted to clinically relevant factors. The clinician assesses latencies, amplitudes, configurations, and conduction velocities. The clinician critiques tracings and determines if repeat recordings are needed. The clinician takes into account the patient’s history, physical examination, NCS, and EMG as needed when interpreting the results. The clinician also considers normal variants. By contrast, with automated devices, a computer scores amplitudes and latencies and determines if tests are normal according to a look-up table. The computer prints an automated interpretation statement for the physician to sign; the computer’s statement is taken from a programmed list of statements.

The NC-Stat Monitor (NeuroMetrix Inc., Waltham, MA) is an automated hand-held device using proprietary technology for conducting NCS. According to the manufacturer, the NC-Stat System is equivalent to larger, more expensive NCS/EMG instruments. The monitor is intended to measure standard nerve conduction parameters such as amplitude, latency, and conduction velocity of the motor as well as sensory nerves. The NC-Stat System has been on the market since 1999 and recently received an updated Food and Drug Administration (FDA) 510(k) clearance. The NC-Stat was initially cleared for marketing by the FDA as a device to measure neuromuscular signals as an adjunct to, and not a replacement for, conventional electrodiagnostic measurements. The updated intended use language is "[t]he NeuroMetrix NC-Stat is intended to stimulate and measure neuromuscular signals that are useful in diagnosing and evaluating systemic and entrapment neuropathies." However, the Code of Federal Regulations clarifies that clearance for marketing under Section 510(k) does not in any way denote official approval of the device. Clearance for marketing does not involve approval for the specific usefulness or evidence of net health outcomes in any specific patient population or disease categories. These health care considerations generally depend on published literature. The NC-Stat System is designed to perform non-invasive NCS for patients with suspected upper and lower extremity disorders/diseases (e.g., carpal tunnel syndrome, low back pain/sciatica, and diabetic peripheral neuropathy).

The available evidence for the NC-Stat monitor is limited in comparison with standard NCS studies and needle EMG. In the largest study of the NC-Stat technology published to date, Katz (2006) established a normal data set for median nerve studies in industrial workers using NC-Stat technology. A total of 1,695 individuals applying for employment at a single heavy industry plant without symptoms of carpal tunnel syndrome (CTS) were studied. Values for median distal motor latency (DML), amplitude, and F-waves were recorded in the dominant limbs. The DML was 3.81 +/- 0.57 milliseconds, with a 95% cut-off value of 4.75 milliseconds. Amplitude of the compound muscle action potential was 0.95 +/- 0.46 mV, reflecting the use of volume conduction by this technology. Most of the workers who were characterized as having borderline, prolonged, or very prolonged distal motor latencies according to the NeuroMetrix automated report actually fell below the 95% cut-off of this independent data analysis. The author concluded that the NC-Stat technology using DML appears to be no more sensitive or specific than a traditionally performed DML for the diagnosis of CTS. Until recently promoted sensory studies using NC-Stat technology are better defined, this technology cannot be recommended for screening or diagnosis of CTS in an industrial population.

A technology assessment of this device, prepared by the Washington State Department of Labor and Industries (Morse, 2006), stated: "The evidence evaluating the use of NC-Stat is most abundant for nerve testing that may be useful to diagnose or screen for conditions at the wrist (i.e., median and ulnar nerve studies). There is very little or no available evidence (high quality, peer-reviewed) supporting the use of NC-Stat and specific biosensors for testing of nerves in the lower extremities. At this time, there is not adequate scientific evidence to conclude that NC-Stat is equivalent to traditional nerve conduction study methods for use in evaluating the functioning of the median, ulnar, peroneal, sural, or tibial nerves. The diagnostic accuracy of NC-Stat is not yet demonstrated in the scientific literature to be equivalent to traditional or gold-standard testing methods. NC-Stat is therefore considered experimental and investigational. NC-Stat is considered controversial as the performance of testing at the point-of-service may not be supported by recommendations of the American Association of Neuromuscular & Electrodiagnostic Medicine."

Work-Loss Data Institute evidence-based guidelines on CTS (2006) stated that NC-Stat monitoring is "not currently recommended."

The Brevio NCS-Monitor (NeuMed Inc., West Trenton, NJ) is a hand-held automated device designed to assess peripheral nerves for conditions such as CTS, diabetic peripheral neuropathy, and tarsal tunnel syndrome. The latest version of the Brevio has a graphical user interface that integrates on-screen prompts to guide a user during an examination. The device utilizes sophisticated firmware with algorithms that seek a maximal compound muscle action potential (CMAP) or sensory nerve action potential (SNAP), plots waveform images in real-time, marks all cursors, and indicates whether or not the latency and amplitude are within normal limits. Upon completion of a full examination, the device can generate a report. The whole examination process (including printing of the report) will take about 15 minutes. There is insufficient evidence to establish the clinical value of this automated NCS studies device.

Schmidt et al. (2011) noted that automated hand-held NCS devices are being marketed for use in the diagnosis of lumbosacral radiculopathy (LSR). In this study, these researchers compared the specificity and sensitivity of a hand-held NCS device for the detection of LSR with standard electrodiagnostic study (EDX). A total of 50 patients referred to a tertiary referral EMG laboratory for testing of predominantly unilateral leg symptoms (weakness, sensory complaints, and/or pain) were included in the investigation; 25 normal "control" subjects were later recruited to calculate the specificity of the automated protocol. All patients underwent standard EDX and automated testing. Raw NCS data were comparable for both techniques; however, computer-generated interpretations delivered by the automated device showed high sensitivity with low specificity (i.e., many false positives) in both symptomatic patients and normal controls. The authors concluded that the automated device accurately recorded raw data, but the interpretations provided were overly sensitive and lacked the specificity necessary for a screening or diagnostic examination.

The American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) states that nerve conduction studies performed independent of needle EMG may only provide a portion of the information needed to diagnose muscle, nerve root, and most nerve disorders.

When NCS is used on its own without integrating needle EMG findings or when an individual relies solely on a review of NCS data, the results can be misleading, and important diagnoses may be missed. Individuals may thus be subjected to incorrect, unnecessary, and potentially harmful treatment interventions.

The American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM, 2005) stated that based on the literature, there are no contraindications to needle EMG in patients with lymphedema or prosthetic joints. In patients with lymphedema, clinical judgment in each individual circumstance should be used in deciding whether the risk of complication is greater than the value of the information to be obtained from the needle electrode examination. Thus, chronic lymphedema (from breast cancer surgery) is not a contraindication to the EMG requirement with nerve conduction velocity studies.

The AANEM (2006) had stated that "the standard of care in clinical practice dictates that using a predetermined or standardized battery of NCSs for all patients is inappropriate." "It is the position of the AANEM that, except in unique situations, NCSs and needle EMG should be performed together in a study design determined by a trained neuromuscular physician." The AANEM explained that standardized nerve conduction studies performed independent of needle EMG studies may miss data essential for an accurate diagnosis. The AANEM position statement (2006) explains that "[t]he performance of or interpretation of NCS separately from the needle EMG component of the testing should clearly be the exception. Nerve conduction studies performed independent of needle EMG may only provide a portion of the information needed to diagnose muscle, nerve root, and most nerve disorders. When the NCS is used on its own without integrating needle EMG findings, or when an individual relies solely on a review of NCS data, the results can be misleading, and important diagnoses may be missed. Moreover, individuals who interpret NCS  data without patient interaction or who rely on studies that have delayed interpretation, who have interpretation made off-site, and who interpret results without complementary information obtained from EMG studies are not meeting the standards outlined in the AANEM policy recommendations."

Nerve conduction studies are essential in diagnosing carpal tunnel syndrome. EMG is a useful optional test for identifying other conditions that may have a similar presentation. However, even for carpal tunnel syndrome, the lack of an EMG study may mean that a diagnosis is missed. The AANEM guidelines explain: "Additionally, patients typically need to have both NCSs and needle EMG to ensure that an underlying medical condition is not missed. For example, in patients with carpal tunnel syndrome (CTS), other disorders can coexist, such as a radiculopathy, brachial plexopathy, or underlying peripheral neuropathy. Alternatively, there may be a problem involving the median nerve but localized at a site more proximal than the wrist. These other problems are far more likely to be misdiagnosed or missed completely if the needle EMG is not performed, and if a physician without the proper skill and training is interpreting the data, making a diagnosis, and establishing a treatment plan. Surgical release of the median nerve at the wrist, a treatment for CTS, would be an inappropriate and unnecessary procedure if the patient does not have CTS. Additionally, NCSs may be normal, but the needle EMG examination may demonstrate abnormalities that identify a more proximal nerve lesion that produces symptoms such as numbness in the hand and that may mimic CTS."

Needle EMG is relatively contraindicated in persons on anti-coagulant therapy with Coumadin (Warfarin) or heparins that cannot be interrupted. Oh (2003) observed that patients with a variety of bleeding disorders may be referred for needle EMG. Oh recommended that the referring physician and the electromyographer examine each case individually, carefully weighing the potential risks and benefits. An increased potential for bleeding may be expected in patients with thrombocytopenia who have a platelet count of less than 50,000/cm³, with a prothrombin time of more than 1.5 to 2 times the control values (International Normalized Ratio of 1.5 to 2.0), or with a partial thromboplastin time greater than 1.5 to 2 times the control value when intravenous heparin therapy is administered (Oh, 2003). Oh (2003) advised that, if the decision is made to perform a needle EMG in such a patient, the clinician should first examine the small, superficial muscles and watch for bleeding problems. The author noted, however, that additionally prolonged local pressure is usually sufficient for hemostasis. This is also the case with patients who have other coagulopathies or who are receiving anti-coagulants (Oh, 2003). Oh (2003) stated that needle examinations should be avoided in patients with hemophilia and other hereditary coagulation disorders unless clotting functions have first been appropriately corrected. Oh (2003) noted that there has been one report of a complication of subcutaneous bleeding secondary to the needle EMG in a patient receiving anti-coagulants and with a partial thromboplastin time greater than twice the control value.

In a discussion of complications from EMG examinations, Kuminga (2001) stated that bleeding tendencies deserve special mention in screening patients for electromyographic examination. Kuminga (2001) stated that specific inquiry in this regard often reveals pertinent information that the patient may not volunteer. To prevent unnecessary complications, the author recommends that the electromyographer consult with the referring physician to weigh the diagnostic benefits against the risks. A patient taking anti-coagulants should have appropriate laboratory tests for bleeding tendency prior to a needle study (Kuminga, 2001). With heparin infusion, partial thromboplastin time should not exceed 1.5 of the control value. With warfarin (Coumadin) therapy, patients should have an international rating (INR) less than 2.0. Kuminga (2001) stated that the same precautions should apply to those with other coagulopathy, such as hemophilia. For thrombocytopenia, unless the platelet count falls below 20,000/mm³, local pressure can usually counter the minimal hemorrhage. The author noted that testing the degree of bleeding tendency with a superficial muscle helps determine the feasibility of further study of deeper muscles, which cannot be compressed adequately to accomplish hemostasis.

Authorities recommend that patients on warfarin should stop taking warfarin 3 days prior to EMG and resume taking it immediately after the test, if permitted by their primary physician. The use of aspirin or aspirin-like medications (such as Plavix (clopidogrel) or Aggrenox (aspirin and dipyridamole)) is not a contraindication to the test.

An assessment of the Brevio by the Washington State Department of Labor and Industries (2007) concluded that "At this time, there appears to be no evidence addressing the diagnostic accuracy of the Brevio nerve conduction system. There is adequate evidence available to evaluate the predicate and predecessor device to the Brevio, the Nervepace. This evidence does not support the accuracy or reliability of Nervepace for use as a diagnostic or screening tool for any condition(s) and specifically for carpal tunnel syndrome."

The American Association of Neuromuscular and Electrodiagnostic Medicine’s report on "Risks in Electrodiagnostic Medicine" (2009) stated that "Needle EMG recording does not introduce electrical current into the body and, therefore, poses no risk of interference with implanted cardiac devices."

Karami-Mohajeri et al. (2014) presented a systematic review of the recent literature on the scientific support of EMG and NCS in diagnosing the exposure and toxicity of organophosphorus pesticides (OP). Specifically, this review focused on changes in EMG, NCS, occurrence of intermediate syndrome (IMS), and OP-induced delayed polyneuropathy (OPIDN) in humans. All relevant bibliographic databases were searched for human studies using the keywords "OP poisoning," "electromyography," "nerve conduction study," and "muscle disorders." Intermediate syndrome usually occurs after an acute cholinergic crisis, while OPIDN occurs after both acute and chronic exposures. Collection of these studies supported that IMS is a neuromuscular junction disorder and can be recorded upon the onset of respiratory failure. Due to the heterogeneity of reports on outcomes of interest such as motor NCS and EMG amplitude in acute cases and the inability to achieve precise estimation of effect in chronic cases, meta-analysis was not helpful to this review. The OPIDN after both acute and low-level prolonged exposures develops peripheral neuropathy without preceding cholinergic toxicity, and the progress of changes in EMG and NCS is parallel with the development of IMS and OPIDN. Persistent inhibition of acetylcholinesterase (AChE) is responsible for muscle weakness, but this is not the only factor involved in the incidence of this weakness in IMS or OPIDN, suggesting that AChE assay is not useful as an index of nerve and muscle impairment. The authors concluded that although several mechanisms for the induction of this neurodegenerative disorder have been proposed, among them oxidative stress and resulting apoptosis can be emphasized. Nevertheless, they stated that there is little synchronized evidence on subclinical electrophysiological findings that limit these investigators from reaching a strong conclusion on the diagnostic or prognostic use of EMG and NCS for acute and occupational exposures to OPs.

In the updated 2004 Position Statement, the AANEM acknowledged the potential for overuse of certain EDX procedures by individual providers, highlighting the need for careful consideration of reimbursement policies for EDX testing. Establishing limits on the number of reimbursed procedures per diagnostic category presents challenges due to the vast number of categories and the lack of substantial scientific literature to support such limits. Instead, a peer review mechanism can be implemented to address instances where EDX test utilization significantly exceeds established norms, such as when testing exceeds the 90th percentile. This approach helps to prevent misuse while allowing physicians the flexibility to exercise their clinical judgment in providing optimal and cost-effective patient care.

The determination of the appropriate number of studies to conduct should rest with the physician performing the EDX evaluation. In cases where testing exceeds the recommended limits—estimated by the AANEM to occur in about 10% of cases—physicians should provide supplementary documentation justifying the additional tests, including explanations of any differential diagnoses that need to be ruled out. It is important to note that EDX testing can establish multiple diagnoses in up to 25% of patients, and the recommendations for a single diagnostic category may not apply in these situations. The number of studies required for multiple diagnoses should not simply be the sum of the studies allowed for each diagnosis, as many tests overlap and can be used to assess different conditions. For instance, the studies for lumbar radiculopathy can often be included in the assessment for polyneuropathy, meaning that the higher number of allowed studies for the more complex diagnosis should guide the testing approach. Additionally, testing an asymptomatic contralateral limb may be necessary to establish normative values for individual patients, as relying solely on general population norms can diminish the sensitivity and specificity of EDX tests.

The American Academy of Orthopaedic Surgeons (AAOS) (Shapiro et al., 2025) published an evidence-based clinical practice guideline to address the diagnosis and treatment of carpal tunnel syndrome (CTS) in adult patients. Recommendations related to electrodiagnostic testing focused on its role in diagnosis relative to clinical assessment tools. The authors note that there are multiple methods by which to diagnose CTS. The guideline scope included evaluation of CTS-6, ultrasonography, nerve conduction velocity and electromyography testing, MRI, and upper limb neurodynamic testing as diagnostic modalities. Diagnostic outcomes assessed included sensitivity, specificity, and the effect of testing on diagnostic probability. The authors reported that CTS-6 demonstrated sensitivity and specificity ranging from 91% to 95% and 91% to 94%, while electrodiagnostic testing demonstrated sensitivity and specificity ranging from 89% to 91% and 83% to 90% in cited studies. Based on the review of the evidence, AAOS provided a strong recommendation for the use of CTS-6 to diagnose CTS, in lieu of routine use of ultrasonography, or NCV/EMG. Additionally, moderate evidence suggests that MRI and upper limb neurodynamic testing should not be used to diagnose CTS.

American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) Recommendations for Electrodiagnostic Medicine

The 2023 American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) Position Statement outlines policy recommendations for electrodiagnostic medicine (EDX), emphasizing its scope and the referral process. Patients are typically referred for EDX studies by neurologists and physiatrists trained in neuromuscular diagnosis, as well as by internists, primary care physicians, neurological and orthopedic surgeons, and other healthcare providers. To aid primary care physicians in determining the necessity of EDX evaluations, the AANEM has published Common Referral Indications. Referrals may come with provisional diagnoses, but many patients are referred based solely on symptoms or clinical findings, with the expectation that the EDX physician will establish a correct diagnosis post-evaluation. After taking a patient history and conducting an examination, the physician formulates a working diagnosis that may evolve during the study, often requiring multiple tests to address both the referral and working diagnoses to reach a final diagnosis. It is important to note that a final diagnosis does not necessarily reflect the complexity of the decision-making process involved. Additionally, EDX testing may not always yield an etiologic diagnosis; when “rule-out” diagnoses are not accepted, only symptomatic diagnoses can be coded, regardless of the evaluation's complexity. EDX studies are primarily conducted by physicians, particularly neurologists and physiatrists, as part of a comprehensive evaluation that includes history-taking, physical examination, and the design, performance, and interpretation of EDX studies, which typically require a minimum of 30 minutes and can extend to over 2 hours in complex cases. The AANEM asserts that non-physician providers, such as physical therapists and chiropractors, lack the necessary training to perform and interpret EMG studies and NCSs, although they may conduct NCS under direct physician supervision.

The AANEM indicates that electrodiagnostic (EDX) testing is utilized to assess the integrity and function of the peripheral nervous system, including most cranial nerves, spinal roots, plexi, and nerves, as well as the neuromuscular junction (NMJ), muscles, and the central nervous system (brain and spinal cord). EDX testing is conducted as part of an evaluation for diagnosis or to monitor an existing condition. EDX studies can provide valuable information to identify normal and abnormal functioning of nerves, muscles, motor and sensory neurons, and the NMJ; localize areas of pathology; characterize the nature of the pathology; determine the distribution and severity of abnormalities; estimate the disease's chronology; assess progression or recovery from abnormal function; assist in diagnosing and prognosing diseases; inform treatment options; monitor treatment responses by offering objective evidence of changes in neuromuscular function; and accurately localize sites for intramuscular injections, such as botulinum toxin.

In a 2025 Position Statement, the AANEM asserts that the proper execution of EDX studies requires specific guidelines ─ first, physicians conducting and interpreting nerve conduction studies (NCSs) and needle electromyography (EMG) must be adequately trained in EDX medicine. Before starting EDX studies, physicians should review referral information and perform a relevant history and physical examination to establish a differential diagnosis that informs the necessary NCS and EMG tests. EDX-trained physicians should directly supervise any NCSs performed by technologists or residents/fellows, and they must interpret the results. Additionally, NCS studies should be conducted and interpreted alongside needle EMG in real-time, adhering to the American Medical Association’s Current Procedural Terminology requirements. The AANEM emphasizes that EDX studies must meet these criteria to ensure quality patient care, as outlined in their Recommended Policy for Electrodiagnostic Medicine. Proper training in EDX is essential, and physicians should have completed residency programs in neurology or physical medicine and rehabilitation, or fellowships in clinical neurophysiology or neuromuscular medicine, to effectively utilize neurophysiological techniques. In-person evaluations are critical for accurate diagnosis, as relying on standardized NCSs without tailoring them to individual patient histories can lead to substandard care. Direct supervision of NCSs is necessary to ensure quality, and the AANEM is concerned about the prevalence of EDX tests that include only NCSs without accompanying needle EMG, which can result in missed diagnoses. The AANEM advocates that all components of EDX testing should be performed or supervised by the same physician on the same date of service to avoid unnecessary duplication of tests and to ensure efficient use of healthcare resources. Ultimately, the AANEM strongly recommends that EDX procedures be conducted by qualified physicians who can provide comprehensive evaluations, as the combination of NCSs and needle EMGs is essential for accurate diagnosis and effective treatment.

Carpal Tunnel Syndrome

The American Association of Neuromuscular & Electrodiagnostic Medicine (Zivkovic et al., 2020) published a quality measure set to provide an introduction to quality measures and outline a quality measurement framework for the electrodiagnosis of carpal tunnel syndrome. Carpal tunnel syndrome was described as a common neuromuscular condition and a major cause of work-related disability, and the measure set was situated within the broader transition of health care from fee-for-service to value-based payment models, in which reporting on quality measures assumed increasing importance. Within this context, the framework outlined process-based measures intended to standardize technical requirements for electrodiagnostic studies, establish electrodiagnostic criteria for diagnosing median neuropathy at the wrist and assessing its severity, and clarify the role of preoperative electrodiagnostic testing. These measures specified that adequate nerve conduction studies included testing of median sensory latency, testing of median distal motor latency, performance of another sensory and motor nerve study in the same extremity, and use of comparison short-segment studies when initial results were normal, and they specified that hand temperature was measured and maintained at or above 32 °C during testing. The framework further specified that electrodiagnostic reports diagnosing median neuropathy at the wrist or severe median neuropathy at the wrist described the electrodiagnostic data supporting the diagnosis and that patients undergoing carpal tunnel release had electrodiagnostic testing performed within 12 months prior to surgery, with defined medical, patient, and system exceptions. The rationale presented was that electrodiagnostic testing augmented clinical diagnosis by providing an objective and quantitative assessment of nerve function with good sensitivity and specificity, that inadequate testing and technical factors such as low limb temperature affected nerve conduction results and could lead to false-positive findings and misdiagnosis, that standardized diagnostic and severity criteria informed treatment options and prognosis, and that preoperative electrodiagnostic testing confirmed diagnosis, evaluated severity and pathophysiology, and excluded alternative or coexisting conditions. The quality measure set stated that implementation of these measures was intended to improve the accuracy of carpal tunnel syndrome diagnosis when electrodiagnostic testing was performed, reduce practice variation, help exclude mimicking conditions, and improve care of patients with carpal tunnel syndrome, with the ultimate goal of improving outcomes.

Combined Sensory Index

The Combined Sensory Index (CSI), also known as the Robinson Index, is an electrodiagnostic measure calculated by summing three sensory latency differences (median-ulnar ring finger, median-radial thumb, and median-ulnar midpalmar), with a value ≥0.9 ms considered abnormal. Originally described by Robinson et al., the CSI has been observed as having superior sensitivity, specificity, and test-retest reliability (Spearman rho = 0.95) compared to its individual component tests for diagnosing carpal tunnel syndrome (CTS). In a prospective study of 408 wrists, nerve conduction studies interpreted using absolute latencies, relative latencies, and the CSI achieved 94% sensitivity for CTS diagnosis. The CSI has also shown prognostic value, with moderate abnormalities (2.5–4.6 ms) correlating with the highest rates of complete symptom resolution after carpal tunnel release. While major society guidelines from the AAN/AANEM/AAPM&R and AAOS recommend comparative sensory testing when standard nerve conduction studies are normal, they do not specifically endorse the CSI by name. The evidence base supporting the CSI, though consistent in its findings, remains modest in volume, consisting primarily of small studies without large-scale multicenter validation. Overall, further research is needed to establish the CSI's role in clinical practice and its potential for broader application in diagnosing CTS (Lew et al., 2000; Padua et al., 2023; Robinson, 2015; Wang et al., 2018).

The "AAOS/ASSH Clinical Practice Guideline Summary Management of Carpal Tunnel Syndrome" (Shapiro et al., 2025) does not include a discussion or recommendation for the Robinson Index or CSI.

Distal Symmetric Polyneuropathy

Distal symmetric polyneuropathy (DSP) is the most common form of peripheral neuropathy and refers to a length‑dependent pattern of nerve injury in which sensory—and sometimes motor—fibers in the longest nerves are affected first, producing symptoms that begin in the feet and progress proximally in a “stocking‑glove” distribution. It is characterized by bilateral, symmetric sensory loss, paresthesias, burning pain, and reduced vibration or temperature sensation; motor weakness may occur in more advanced stages. DSP has multiple potential etiologies, including diabetes (the most common cause), alcohol use disorder, nutritional deficiencies, certain medications or toxins, and systemic diseases. Pathophysiologically, it involves axonal degeneration and/or demyelination due to metabolic, ischemic, or toxic insults. Diagnosis is clinical and supported by nerve conduction studies (NCS). Management focuses on identifying and treating the underlying cause and managing neuropathic symptoms.

Callaghan et al. (2015) noted that peripheral neuropathy is a highly prevalent and morbid condition affecting 2% to 7% of the population. Patients frequently experience pain and are at risk of falls, ulcerations, and amputations. These investigators reviewed recent diagnostic and therapeutic advances in DSP. Current evidence supports limited routine laboratory testing in patients with DSP. Patients without a known cause should undergo a complete blood cell count, comprehensive metabolic panel, vitamin B12 measurement, serum protein electrophoresis with immune-fixation, fasting glucose measurement, and glucose tolerance test. The presence of atypical features such as asymmetry, non-length dependence, motor predominance, acute or sub-acute onset, and prominent autonomic involvement should prompt a consultation with a neurologist or neuromuscular specialist. Electro-diagnostic tests and magnetic resonance imaging (MRI) of the neuro-axis contribute substantial cost to the diagnostic evaluation, but evidence supporting their use is lacking. Strong evidence supports the use of tricyclic anti-depressants, serotonin norepinephrine reuptake inhibitors, and voltage-gated calcium channel ligands in the treatment of neuropathic pain. More intensive glucose control substantially reduces the incidence of DSP in patients with type 1 diabetes but not in those with type 2 diabetes. The authors concluded that the opportunity exists to improve guideline-concordant testing in patients with DSP. Moreover, they stated that the role of electro-diagnostic tests needs to be further defined, and interventions to reduce MRI use in this population are needed. Furthermore, they noted that even though several effective medications exist for neuropathic pain treatment, pain is still under-recognized and under-treated; new disease-modifying medications are needed to prevent and treat peripheral neuropathy, especially in type 2 diabetes.

The updated 2024 AANEM Policy Statement on Electrodiagnosis for Distal Symmetric Polyneuropathy (DSP) highlights that DSP is a prevalent reason for referrals to electrodiagnostic testing, with diabetes mellitus being the most common cause in developed countries, accounting for 30-80% of cases. Despite over 200 documented causes, DSP was not fully defined until 2005, when systematic literature analysis and expert consensus established its diagnostic criteria. EDX testing, which includes nerve conduction studies (NCS) and needle electromyography (EMG), is essential for diagnosing DSP, determining whether axonal or myelin involvement is predominant, and identifying the underlying etiology. The accuracy of clinical history and physical examination in diagnosing DSP is limited, as evidenced by studies showing that EDX testing can reveal alternative diagnoses in a significant percentage of cases. EDX testing is crucial for establishing primary and alternative diagnoses, assessing the severity and duration of the condition, evaluating risks for associated complications, and determining the effects of medications and toxic exposures. While cost and patient comfort are important considerations, the cost-effectiveness of EDX is often justified by the valuable diagnostic information it provides. EDX testing should be considered when standard evaluations do not indicate a likely etiology, when symptoms are moderate to severe, or when atypical presentations or rapid progression of symptoms occur. However, it may be of low yield in cases with mild symptoms, known causes, or when there is little suspicion of coexisting nerve disorders. Ultimately, while EDX testing is vital for many patients with DSP, it should be tailored to individual cases based on a thorough clinical history and physical examination.

Diabetic Sensorimotor Polyneuropathy

Schamarek and colleagues (2016) noted that subclinical inflammation has been implicated in the development of diabetic sensorimotor polyneuropathy (DSPN), but studies using electrophysiological assessment as outcomes are scarce. These investigators examined associations of biomarkers reflecting different aspects of subclinical inflammation with motor and sensory NCV in individuals with diabetes. Motor and sensory NCV was assessed in individuals with recently diagnosed type 2 (n = 352) or type 1 diabetes (n = 161) from the baseline cohort of the observational German Diabetes Study; NCV sum scores were calculated for median, ulnar and peroneal motor as well as median, ulnar and sural sensory nerves. Associations between inflammation-related biomarkers, DSPN and NCV sum scores were estimated using multiple regression models. In type 2 diabetes, high serum interleukin (IL)-6 was associated with the presence of DSPN and reduced motor NCV. Moreover, higher levels of high-molecular weight (HMW) adiponectin, total adiponectin and their ratio were associated with prevalent DSPN and both diminished motor and sensory NCV, whereas no consistent associations were observed for C-reactive protein (CRP), IL-18, soluble intercellular adhesion molecule-1 and E-selectin. In type 1 diabetes, only HMW and total adiponectin showed positive associations with motor NCV. The authors concluded that these findings pointed to a link between IL-6 and both DSPN and slowed motor NCV in recently diagnosed type 2 diabetes. They stated that the reverse associations between adiponectin and NCV in type 1 and type 2 diabetes are intriguing, and further studies should explore whether they may reflect differences in the pathogenesis of DSPN in both diabetes types.

NC-stat DPNCheck

Chatzikosma and colleagues (2016) evaluated the utility of automated NCS of the sural nerve with a new portable device for the diagnosis of diabetic polyneuropathy (DPN) in patients with type 2 diabetes mellitus (T2DM). This study included 114 T2DM patients (58 men) with a mean age of 64.60 ± 8.61 years. Exclusion criteria were B12 depletion, alcohol abuse, and other causes of peripheral neuropathy (PN). The reference method was the Neuropathy Disability Score (NDS) with a threshold NDS greater than or equal to 3. Sural nerve automated NCS was performed with the portable NC-stat DPNCheck device. Sensory nerve conduction velocity and sensory nerve action potential amplitude were measured bilaterally. Automated NCS was considered abnormal when greater than or equal to 1 of the 2 aforementioned neurophysiological parameters was abnormal in at least 1 leg. Examination with NC-stat DPNCheck exhibited 90.48% sensitivity, 86.11% specificity, 79.17% positive predictive value (PPV), and 93.94% negative predictive value (NPV). The positive likelihood ratio (LR+) was 6.51, and the negative likelihood ratio (LR-) was 0.11. Sural nerve automated NCS with the NC-stat DPNCheck device exhibits high sensitivity and specificity for the diagnosis of DPN in T2DM. The authors concluded that the findings of this study suggested that sural nerve automated NCS with the NC-stat DPNCheck device exhibited high sensitivity and specificity for the diagnosis of clinical DPN in T2DM. This high diagnostic performance suggested that the test may prove useful as a screening tool for DPN, with particular utility in the exclusion of this condition. The present results added to the increasing appreciation of the importance that automated NCS may have in improving the diagnosis of DPN, including in the primary health care setting.

The authors stated that this study had several drawbacks. First, they included patients from a tertiary care setting, and therefore the results may not be directly applicable to the general diabetic population. Second, they did not confirm the diagnosis of DPN by classical NCS. Lastly, they only studied patients with T2DM, and so more experience with T1DM is needed.

Vogt and colleagues (2017) stated that scant information is available about the prevalence of DPN, as well as the applicability of screening tools in sub-Saharan Africa. These investigators examined these issues in Zanzibar (Tanzania). A total of 100 consecutive diabetes patients were included in this study. These researchers also investigated self-reported numbness of the lower limbs, the 10-point monofilament test, the Sibbald 60-s Tool, and NCS using an automated handheld point-of-care device, the NC-stat DPNCheck. The mean age was 54 years, 90% had T2DM, and the average disease duration was 9 years. Mean hemoglobin A1c (HbA1c) was 8.5%, blood pressure was 155/88 mmHg; 62% reported numbness, 61% had a positive monofilament test, and 79% had a positive Sibbald tool; NCS defined neuropathy in 45% of the patients. Only the monofilament showed appreciable concordance with the NCS, Cohen's κ = 0.43. The authors concluded that these findings suggested the utility of the monofilament as a screening tool for DPN and the NC-stat DPNCheck in cases of diagnostic uncertainty or for research purposes in a low-resource setting. Moreover, they stated that in order to address the associated risk of ulcers and amputations, a prospective study in this diabetes population would be of great value.

Hamasaki and Hamasaki (2017) stated that currently, no international diagnostic criteria for diabetic neuropathy (DN) have been established. Recently, a novel point-of-care (POC) sural nerve conduction device (DPNCheck) has been developed. These investigators examined associations between DN and clinical parameters related to the development and progression of DN by using this novel device. These researchers conducted a retrospective observational study in patients with diabetes whose sural nerve functions were measured using DPNCheck between January 2015 and October 2016. Multiple and logistic regression analyses were conducted to evaluate the associations of sural nerve conduction velocity (SNCV) and amplitude (SNAP) with clinical parameters related to DN. A total of 740 patients were enrolled in this study. At baseline, 211 patients were diagnosed with DN by using DPNCheck. The sensitivity, specificity, and LR+ of DPNCheck compared with ankle reflex as a reference were 81%, 46%, and 1.5, respectively. Of these, 182 patients were followed up for approximately 1 year to measure changes in SNCV and SNAP. Both SNCV and SNAP were inversely associated with the duration of diabetes, plasma glucose levels, and HbA1c levels at baseline, whereas these were positively associated with the ankle-brachial index (ABI). Logistic regression analysis revealed that poor glycemic control was associated with an increased risk of reduction in both SNCV [odds ratio (OR) = 1.570; 95% CI: 1.298 to 1.898; p < 0.001] and SNAP (OR = 1.408; 95% CI: 1.143 to 1.735; p = 0.001), and longer duration of diabetes was also significantly associated with an increased risk of reduction in both SNCV (OR = 1.058; 95% CI: 1.032 to 1.084; p < 0.001) and SNAP (OR = 1.049; 95% CI: 1.019 to 1.079; p = 0.001). The authors concluded that the findings of this study suggested that early initiation of treatment for diabetes is essential for preventing the progression of DN. The factors associated with DN were duration of diabetes, glycemic control, and ABI. Moreover, they stated that this study also showed the utility of DPNCheck in clinical practice, which may be useful as a screening tool to identify DN.

The authors stated that this study had several drawbacks. First, there were some missing values because of the study design. Second, these researchers did not measure SNCV and SNAP bilaterally. The mean duration of diabetes of patients with DN was 17.4 ± 10.1 years in the present study; thus, most patients were expected to have similar bilateral sural nerve impairment. Third, these investigators did not evaluate patients’ symptoms and certain diagnostic indicators other than ankle reflex, such as vibration perception threshold. They could not evaluate the diagnostic accuracy of DPNCheck because clinical findings, symptoms, signs, and standard nerve conduction study were insufficient. However, as shown in previous studies, DPNCheck had a high sensitivity and a relatively low specificity in this study. This device can rule out the presence of DN if the test is negative; however, it is not suitable for the definitive diagnosis of DN. Fourth, there should have been heterogeneity of physical examination between diabetologists in this study. Fifth, post-hoc sample size calculation was also a limitation. Finally, according to the National Health and Nutrition Survey in 2008, the prevalence of DN in Japanese patients with diabetes was 11.8%; thus, the authors could not generalize the results to other primary care populations. The discrepancy in the prevalence of DN may be attributed to the clinical setting, which was a clinic specializing in the management of diabetes. Despite these drawbacks, these researchers demonstrated that sural nerve functions evaluated by the novel device DPNCheck were significantly associated with glycemic control and arteriosclerosis in patients with diabetes. To ensure these associations and evaluate the effects of diabetes treatment on DN, additional studies, preferably randomized controlled trials (RCTs) that include peripheral nerve function as a primary outcome, are needed.

Hirayasu and associates (2018) noted that studies on a novel POC device (POCD) for nerve conduction study called DPNCheck have been limited to Westerners. These investigators clarified Japanese normal limits of nerve action potential amplitude (Amp) and conduction velocity by DPNCheck (investigation I), and the validity of DPNCheck to identify diabetic symmetric sensorimotor polyneuropathy (DSPN; investigation II). For investigation I, a total of 463 non-neuropathic Japanese participants underwent DPNCheck examinations. Regression formulas calculating the normal limits of Amp and conduction velocity (Japanese regression formulas [JRF]) were determined by quantile regression and then compared with regression formulas of individuals from the USA (USRF). For investigation II, in 92 Japanese diabetes patients, "probable DSPN" was diagnosed, and nerve conduction abnormalities (NCA1: 1 or more abnormalities, and NCA2: 2 abnormalities in Amp and conduction velocity) were determined. Validity of NCAs to identify "probable DSPN" was evaluated by determining sensitivity, specificity, reproducibility (kappa-coefficient), and the area under the curve of receiver operating characteristic curves. For investigation I, JRF was different from USRF, and normal limits by JRF were higher than those of USRF. The prevalence of Amp abnormality calculated by JRF was significantly higher than that of USRF. For investigation II, the sensitivity, specificity, and reproducibility of NCA1 and NCA2 judged from JRF were 85%, 86%, and 0.57, and 43%, 100%, and 0.56, respectively. These values of JRF were higher than those of USRF. The area under the curve of JRF (0.89) was larger than USRF (0.82). The authors concluded that a significant difference in the normal limits of nerve conduction parameters by DPNCheck between Japanese and USA individuals was suggested; validity to identify DSPN of NCAs might improve by changing the judgment criteria from USRF to JRF.

The authors stated that the main drawback of their studies was that the number of diabetes patients was not so large (n = 92). Thus, in order to confirm the improved accuracy to identify DPN using the POCD for NCS by using Japanese normal limits instead of USA normal limits, a larger-scale study is needed.

Nerve Conduction Studies for Cubital Tunnel Syndrome

Assmus et al. (2011) stated that cubital tunnel syndrome (CubTS) is the second most common peripheral nerve compression syndrome. In German-speaking countries, CubTS is often referred to as sulcus ulnaris syndrome (retrocondylar groove syndrome). This term is anatomically incorrect, since the site of compression comprises not only the retrocondylar groove but the cubital tunnel, which consists of three parts: the retrocondylar groove, partially covered by the cubital tunnel retinaculum (lig. arcuatum or Osborne ligament), the humeroulnar arcade, and the deep flexor/pronator aponeurosis. According to Sunderland, CubTS can be differentiated into a primary form (including anterior subluxation of the ulnar nerve and compression secondary to the presence of an anconeus epitrochlearis muscle) and a secondary form caused by deformation or other processes of the elbow joint. The clinical diagnosis is usually confirmed by nerve conduction studies.

Liu et al. (2015) examined the lesions' location and prognosis of cubital tunnel syndrome (CubTS) by routine motor nerve conduction studies (MNCSs) and short-segment nerve conduction studies (SSNCSs, inching test). A total of 30 healthy subjects were included, and 60 ulnar nerves were studied by inching studies for normal values; 66 patients who were diagnosed with CubTS clinically were evaluated bilaterally by routine MNCSs and SSNCSs. Follow-up for 1 year included the collection of information on brief complaints, clinical symptoms, and physical examination. A total of 66 patients were included; 88 nerves were abnormal by MNCS, while 105 were abnormal by the inching studies. The segment from the medial epicondyle to 2 cm above the medial epicondyle was the most common segment to be detected abnormally (59.09%, p < 0.01); 22 patients were followed up, and 17 patients' symptoms improved. Most of the patients were treated with drugs and modification of bad habits. The authors concluded that SSNCSs could detect lesions of compressive neuropathy in CubTS more precisely than routine motor conduction studies; SSNCSs could diagnose CubTS more sensitively than routine motor conduction studies. These investigators also found that the segment from the medial epicondyle to 2 cm above the medial epicondyle was the most vulnerable place for ulnar nerve compression, and patients exhibited a better prognosis if they had abnormal motor nerve conduction time only, but not amplitude, in compressed lesions compared to those who had abnormalities in both velocity and amplitude. These researchers stated that the findings of this study suggested that SSNCSs were a practical method for detecting ulnar nerve compressed neuropathy and were sensitive in diagnosing CubTS. The compound muscle action potentials (APs) by SSNCSs may predict the prognosis of CubTS.

Roberts et al. (2015) noted that ulnar nerve compression at the elbow is the second most common neuropathy of the upper limb. It has been suggested that nerve conduction tests are required to correctly make the diagnosis. These researchers examined if patients with normal nerve conduction testing benefited from surgical release of the ulnar nerve. A total of 56 patients with symptoms of ulnar nerve compression at the elbow were evaluated prospectively. All patients underwent electrophysiology testing followed by ulnar nerve decompression irrespective of the results of the electrophysiology testing. Functional scores using the Quick Disabilities of the Arm, Shoulder and Hand (DASH) and PEM score were collected up to 12 months post-surgery. No difference was found between the group with normal and the group with abnormal electrophysiology studies. The authors concluded that patients who clinically have ulnar nerve compression still benefit from ulnar nerve decompression despite normal nerve conduction tests.

The American Association of Electrodiagnostic Medicine (AANEM, 2015) practice parameter guidelines state that if ulnar sensory or motor NCSs are abnormal, further NCSs should be carried out to exclude a diffuse process. 

Liu et al. (2016) stated that the appropriate elbow position for SSNCS to diagnose CubTS is still controversial. In a cross-sectional study, these researchers examined the effect of different elbow positions at full extension and 70° flexion on SSNCS in CubTS. The clinical data of seventy elbows from 59 CubTS patients (between September 2011 and December 2014) in the Peking University First Hospital were included as the CubTS group, and 30 healthy volunteers were included as the healthy group. SSNCS were conducted in all subjects at elbow full extension and 70° elbow flexion. Paired non-parametric tests, bi-variate correlation, Bland-Altman, and Chi-squared test analyses were used to compare the effectiveness of elbow full extension and 70° flexion elbow positions on SSNCS in CubTS patients. Data of the upper limit were calculated from the healthy group, and abnormal latency was judged accordingly. The latency and compound muscle action potential (CMAP) of each segment at 70° elbow flexion by SSNCS were compared with the full extension position; no statistically significant differences were found (all p > 0.05). Latency and CMAP of each segment at elbow full extension and 70° flexion were correlated (all p < 0.01), except for the latency of the segment 4 cm to 6 cm above the elbow (p = 0.43) and the latency (p = 0.15) and the CMAP (p = 0.06) of the segment 2 cm to 4 cm below the elbow. Bi-variate correlation and Bland-Altman analysis proved the correlation between elbow full extension and 70° flexion. Especially in segments across the elbow (2 cm above the elbow and 2 cm below it), latency at elbow full extension and 70° flexion were strongly directly associated (r = 0.83, p < 0.01; r = 0.55, p < 0.01), and so did the CMAP (r = 0.49, p < 0.01; r = 0.72, p < 0.01). There was no statistically significant difference in the abnormality of each segment at full extension as measured by SSNCS compared with that at 70° flexion (p > 0.05, respectively). The authors concluded that there was no statistically significant difference in the diagnosis of CubTS with the elbow at full extension compared with that at 70° flexion during SSNCS. They suggested that the elbow position at full extension can also be used during SSNCS.

Power et al. (2019) noted that CubTS has a spectrum of presentations ranging from mild paresthesia to debilitating numbness and intrinsic atrophy. Commonly, the classification of severity relies on clinical symptoms and slowing of conduction velocity across the elbow. However, changes in CMAP amplitude more accurately reflect axonal loss. These investigators hypothesized that CMAP amplitude would better predict functional impairment than conduction velocity alone. A retrospective cohort of patients who underwent a surgical procedure for CubTS over a 5-year period was included in the study. All patients had electrodiagnostic testing performed at the authors’ institution. Clinical and electrodiagnostic variables were recorded. The primary outcome was pre-operative functional impairment, defined by grip and key pinch strength ratios. Multi-variable regression identified which clinical and electrodiagnostic variables predicted pre-operative functional impairment. A total of 83 patients with a mean age of 57 years (75% men) were included in the study. The majority of patients (88%) had abnormal electrodiagnostic studies; 54% had reduced CMAP amplitude, and 79% had slowing of conduction velocity across the elbow (recorded from the first dorsal interosseous). On bi-variate analysis, older age and longer symptom duration were significantly associated (p < 0.05) with reduced CMAP amplitude and slowing of conduction velocity across the elbow, whereas body mass index (BMI), laterality, a primary surgical procedure compared with a revision surgical procedure, DASH questionnaire scores, and visual analog scale (VAS) scores for pain were not. Multi-variable regression analysis demonstrated that reduced first dorsal interosseous CMAP amplitude independently predicted the loss of pre-operative grip and key pinch strength, and that slowed conduction velocity across the elbow did not. The authors concluded that reduced first dorsal interosseous amplitude predicted pre-operative weakness in grip and key pinch strength, and isolated slowing of conduction velocity across the elbow did not; CMAP amplitude was a sensitive indicator of axonal loss and an important marker of the severity of CubTS. It should be considered when counseling patients regarding their prognosis and determining the necessity and timing of operative intervention.

Shubert et al. (2021) stated that electrodiagnostic studies (EDX) serve a prominent role in the diagnostic work-up of CubTS; however, their reported sensitivity varies widely. These investigators examined the sensitivity of EDX in a cohort of patients who responded well to surgical cubital tunnel release (CBTR), and whether the implementation of the Association of Neuromuscular and Electrodiagnostic Medicine (AANEM) criteria would improve the sensitivity. These researchers identified 118 elbows with clinical CubTS who had pre-operative EDX and underwent CBTR. The EDX diagnoses were CubTS, ulnar neuropathy (UN), and normal ulnar nerves. These investigators divided the 118 elbows into those that received above-elbow stimulation (XE group) and those that did not (non-XE group). They calculated the sensitivities for all groups and re-interpreted the results according to the AANEM guidelines. Cubital tunnel release provided significant relief in 93.6% of the elbows. Based on the EDX reports, 11% of patients had clear CubTS, 23% had UN, and 66% showed no UN. The sensitivities were 11.7% for CubTS and 34.2% for any UN. In the XE group, the sensitivity of the EDX reports for CubTS and UN climbed to 33.3% and 58.3%, respectively. When the authors calculated the across-elbow motor nerve conduction velocity, the sensitivity for CubTS and UN was 87.5% and 100%, respectively. The XE and non-XE groups showed no difference except for sex, bilaterality, concomitant carpal tunnel release, and obesity (p < 0.05). The authors concluded that implementing AANEM guidelines resulted in significant improvement in the correlation of clinical and electrodiagnostic findings of CubTS.

Liu et al. (2020) noted that the first dorsal interosseous muscle (FDI) is usually innervated by the deep branch of the ulnar nerve; however, as was first noted by Sunderland in 1946, some individuals have variable innervation of the FDI. These investigators examined the incidence of variable innervation of the FDI by using electrophysiological examination and further evaluated the relevance of this variation in patients with CubTS. This study included 211 patients who underwent peripheral nerve surgery in Huashan Hospital, Fudan University, between October 2012 and February 2014. The patients were divided into three groups: the carpal tunnel syndrome (CTS) group, the CubTS group, and the control group. During surgery, electromyography (EMG) was used to determine FDI variation, and a hand function instrument was used to estimate the pinch strength between the thumb and index finger in both hands of the CubTS patients. The EMG showed that 22 of the patients enrolled had variable innervation of the FDI. Compared with the CTS group and the control group, the incidence of variable innervation of the FDI was much higher in the CubTS group (p < 0.05). Patients under the age of 60 years in the CubTS group were more likely to have the variation (p = 0.043). A higher pinch strength ratio was significantly associated with variable innervation of the FDI in the CubTS patients (p = 0.030). The authors concluded that by means of EMG, the findings of this study demonstrated that the variable innervation of the FDI could be innervated by the median nerve. In the CubTS patients, the higher incidence of FDI variation was possibly related to age, and this variation might lead to a better prognosis for CubTS patients.

Nerve Conduction Studies for Evaluation of Cervical Radiculopathy

The American Association of Electrodiagnostic Medicine (1998), supported by the American Academy of Physical Medicine and Rehabilitation (1999), recommends that electrodiagnostic (EDX) consultations for patients suspected of having cervical radiculopathy should include a thorough clinical history and physical examination to ensure that laboratory findings are interpreted within the appropriate clinical context. Given that entrapment neuropathies, such as carpal tunnel syndrome (CTS) and ulnar neuropathy, can mimic cervical radiculopathy, the consultation should also involve a screening evaluation for these conditions. If EDX findings indicate cervical radiculopathy, the consultant should identify the specific affected nerve root and assess the severity and chronicity of the condition. The following guidelines for EDX studies aim to provide laboratory confirmation of cervical radiculopathy, based on scientific literature supporting the use of needle electromyography (EMG) and nerve conduction studies (NCS) for evaluating cervical radiculopathy and upper extremity entrapment neuropathies. Recommendations are classified as either Guidelines or Options, depending on the quality and consistency of supporting evidence, as well as the potential harms, benefits, and costs. Key guidelines include performing needle EMG on at least one muscle innervated by the C5 to T1 spinal roots in the symptomatic limb, examining cervical paraspinal muscles as appropriate, and conducting at least one motor and one sensory NCS in the clinically involved limb to check for concomitant polyneuropathy or nerve entrapment. If abnormalities are found, further evaluations may be warranted. Options include performing needle EMG on contralateral muscles to differentiate between bilateral radiculopathy and other conditions, conducting F-wave studies for suspected C8 or T1 radiculopathy, cervical nerve root stimulation to identify radiculopathy, and H-reflex studies of the flexor carpi radialis to assess C6 and C7 nerve root pathology.

Nerve Conduction Studies for Evaluation of COVID-19 Associated Neuromuscular Disorders

In a cross-sectional study, Khalil et al. (2025) described electrodiagnostic (EdX) findings of neuromuscular disorders (NMD) associated with COVID-19 infection. Patients with a history of COVID-19 infection and neuromuscular symptoms were included. After documenting the demographics, a detailed examination, as well as nerve conduction studies (NCS) and electromyography (EMG), were carried out. Descriptive statistics were determined. Polyneuropathy was the most common electrophysiological diagnosis (n = 22, 40%), and among these, Guillain-Barré syndrome (GBS) was the most common (n = 13, 23.6%). Patients with a history of invasive ventilation had 2.5 times the risk of developing a myopathic disorder (odds ratio [OR] 2.5; 95% CI: 0.6 to 9.9) and 2.6 times the risk of developing a neuropathic disorder compared to those who did not require invasive ventilation (OR 2.6; 95% CI: 0.8 to 8.5). Polyneuropathy is the most common NMD associated with COVID-19 infection. Patients with a history of invasive ventilation following COVID-19 were susceptible to developing neuropathic disorders. The authors concluded that further investigations are needed to establish the causality of this correlation.

The authors stated that this trial had two main drawbacks. First, the functional status of the patients was not evaluated. Second, because of the limited data and a small sample size, these researchers could not comment on the temporal relationship of these disorders with COVID-19 infection.

Nerve Conduction Studies for Evaluation of Peyronie's Disease

The American Urologic Association’s guideline on Peyronie’s disease (Nehra et al., 2015) had no recommendation for nerve conduction studies. Furthermore, an UpToDate review on “Peyronie's disease: Diagnosis and medical management” (Brant et al, 2025) has no recommendation for nerve conduction studies in the workup of Peyronie’s disease.

Nerve Conduction Studies for Evaluation of Spinal Muscular Atrophy

There is no current role for using nerve conduction velocity studies (NCV) to follow the clinical progression of patients with spinal muscular atrophy (SMA). The utility of measuring compound muscle action potentials and other metrics of motor unit function in patients with SMA to gauge response to disease modifying therapy are under investigation. 

Ogata et al. (2025) aimed to identify sensitive response measures for evaluating treatment efficacy in patients with spinal muscular atrophy (SMA). The authors compared electrodiagnostic (EDX) measures, such as compound muscle action potential (CMAP), motor unit number index (MUNIX), and motor unit size index (MUSIX), with traditional functional assessments, including the Hammersmith Functional Motor Scale Extended (HFMSE), Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND), and the Revised Upper Limb Module (RULM). A retrospective chart review was conducted on 16 non-ambulatory, late-onset SMA children seen between January 2017 and June 2024, analyzing motor nerve conduction study (NCS) recordings from the right median-abductor pollicis brevis (APB) and ulnar-abductor digiti minimi (ADM) nerve muscle pairs alongside functional scores using Spearman correlation and a generalized linear mixed model (GLMM). The results indicated that EDX measures were significantly lower in SMA children compared to healthy, age-matched controls (p < 0.05). Notably, median APB CMAP amplitudes showed moderate to strong correlations with CHOP-INTEND (r = 0.64, p < 0.05) and RULM (r = 0.77, p < 0.05) scores, with the GLMM revealing a significant decrease in APB CMAP over time (Beta = -0.02, p < 0.05) in the non-treatment group compared to the treatment group. Additionally, HFMSE scores exhibited a declining trend in patients receiving only risdiplam. The authors concluded that median APB CMAP amplitude is sensitive in capturing treatment response, highlighting the need for a prospective study comparing nusinersen and risdiplam in a larger, clinically diverse cohort with extended follow-up.

Bjelica et al. (2025) conducted a multicenter, binational observational study to assess changes in compound muscle action potential (CMAP) amplitude in adults with spinal muscular atrophy (SMA) receiving nusinersen treatment and its relationship with improvements in motor function. The authors evaluated median, ulnar, and peroneal CMAP over a follow-up period of up to 4.5 years using linear mixed models, while motor function was measured with the Revised Upper Limb Module (RULM) and the Hammersmith Functional Motor Scale Expanded (HFMSE). The analysis included 78 patients (27 ambulatory and 51 non-ambulatory), revealing that a baseline ulnar CMAP ≥ 2.0 mV effectively distinguished SMA type 3 from type 2 with 91.3% sensitivity and 88.9% specificity (AUC 0.96, 95% CI 0.92-1.0), while a baseline median nerve CMAP ≥ 6.5 mV demonstrated 91.7% sensitivity and 77.3% specificity (AUC 0.84, 95% CI 0.72-0.96). However, no significant changes in median, ulnar, or peroneal CMAP amplitudes were observed over time (p > 0.05), and CMAP trajectories did not differ between SMA types 2 and 3 (p > 0.05). Additionally, there were no significant differences in changes in RULM or HFMSE scores at any time point between patients with baseline median nerve CMAP < 5 mV and those with CMAP ≥ 5 mV (p > 0.05). The study found no significant correlations between changes in median nerve CMAP and HFMSE or RULM scores (p > 0.05). The authors concluded that CMAP amplitudes remained stable during nusinersen treatment, with no differences in trajectories between SMA types 2 and 3, suggesting that while CMAP amplitude correlates with disease severity, it may not be a sensitive biomarker for treatment response in adult SMA patients.

Nerve Conduction Velocity in Relation to Blood Lead Levels

Yu and colleagues (2019) stated that previous studies relating nervous activity to blood lead (BL) levels have limited relevance because, over time, environmental and occupational exposure substantially dropped. These investigators examined the association of heart rate variability (HRV) and median nerve conduction velocity (NCV) with BL using the baseline measurements collected in the Study for Promotion of Health in Recycling Lead (NCT02243904). In 328 newly hired men (mean age of 28.3 years; participation rate 82.7%), these researchers derived HRV measures (power expressed in normalized units (nu) in the high-frequency (HF) and low-frequency (LF) domains, and LF/HF) prior to long-term occupational lead exposure. Five-minute ECG recordings, obtained in the supine and standing positions, were analyzed by Fourier transform or auto-regressive modeling, using Cardiax software. Motor NCV was measured at the median nerve by a hand-held device (Brevio Nerve Conduction Monitoring System, NeuMed, West Trenton, NJ). BL was determined by inductively coupled plasma mass spectrometry. Mean BL was 4.54 µg/dL (inter-quartile range [IQR] 2.60 to 8.90 µg/dL). Mean supine and standing values of LF, HF, and LF/HF were 50.5 and 21.1 nu and 2.63, and 59.7 and 10.9 nu and 6.31, respectively. Orthostatic stress decreased HF and increased LF (p < 0.001); NCV averaged 3.74 m/s. Analyses across thirds of the BL distribution and multi-variable-adjusted regression analyses failed to demonstrate any association of HRV or NCV with BL. The authors concluded that at the exposure levels observed in this study, autonomous nervous activity and NCV were not associated with BL.

The authors stated that this study had several drawbacks. First, findings in workers could not be extrapolated to the general population because of the so-called healthy worker effect. Second, although this study population was ethnically diverse, it included few Asians and no women. Finally, a potential drawback of this study was that these investigators did not measure bone lead as an exposure marker. Approximately 95% of the total body burden of lead is present in the skeleton, and measurement of bone lead levels would provide a more accurate measure of the internal dose. However, blood lead reflects both recent exogenous exposure and endogenous redistribution of the lead stored in bone.

Neuromuscular Junction Testing and Botulism

Boccagni et al. (2021) highlight that neurophysiological patterns in patients with foodborne botulism are seldom documented after the acute phase, presenting data from a significant Italian outbreak where patients were evaluated at various time points following poisoning. The study involved eighteen male patients (mean age 47 ± 8.4 years) who underwent 22 clinical and neurophysiological assessments, including resting compound muscle action potential (CMAP) amplitude, postexercise CMAP amplitude, CMAP changes after high-frequency repetitive nerve stimulation (HFRNS), and motor unit action potentials (MUAPs) during the acute (4-8 days post-poisoning; 5 patients), early post-acute (32-39 days post-poisoning; 5 patients), and late post-acute (66-80 days post-poisoning; 12 patients) phases. Results showed that reduced CMAP amplitudes were present in 100%, 20%, and 17% of patients across the three phases, while abnormal postexercise CMAP facilitation was observed in 100%, 40%, and none of the patients, and pathological incremental responses to HFRNS were found in 80%, 50%, and 8% of patients, respectively. Significant differences were noted in baseline CMAP amplitudes, postexercise CMAP facilitation, and CMAP increases in response to HFRNS between the acute and post-acute phases, with small MUAPs detected in all patients during the acute and early post-acute phases and in half of the patients in the late post-acute phase. The findings indicate that neurophysiological characteristics of foodborne botulism vary significantly depending on the timing of the evaluation, suggesting that different neurophysiological techniques are necessary to support a diagnosis in the post-acute phase.

According to the Centers for Disease Control and Prevention’s “Clinical Guidelines for Diagnosis and Treatment of Botulism” (Rao et al., 2021), routine laboratory tests, including complete blood counts, cerebrospinal fluid (CSF) examination, and radiologic studies, typically yield normal results in botulism patients, unlike Guillain-Barré syndrome, where CSF protein levels are often elevated by the second week of illness. Mild increases in CSF protein are infrequently reported in botulism cases. Brain imaging may help rule out brainstem strokes that could cause similar symptoms, and the Tensilon (edrophonium) test, used for diagnosing myasthenia gravis, is generally negative in botulism patients, although minimal responses have been noted. Electrodiagnostic studies, such as repetitive nerve stimulation (RNS), electromyography (EMG), and nerve conduction studies (NCSs), can clarify the cause of muscle weakness, with RNS assessing motor nerve response and EMG evaluating electrical activity in muscles. Distinctive findings in botulism include increased compound motor nerve action potential amplitude with RNS at 30–50 Hz, fibrillation, decreased muscle unit recruitment, and reduced motor-evoked amplitude on NCS, although early in the disease, results may be normal. These tests have limitations, including operator dependency, technical challenges, and the need for specialized training and equipment, and they can be painful for patients. Clinicians should be aware that paralyzed and intubated patients remain conscious unless sedated, necessitating clear communication about the testing process. The sensitivity and specificity of these electrodiagnostic methods for diagnosing botulism are not well established, and findings may overlap with other neuromuscular diseases. While electrodiagnostic studies can aid in diagnosing suspected botulism, especially in unclear cases, they are rarely needed during outbreaks with clear clinical presentations. However, they can help differentiate botulism from other conditions like myasthenia gravis or Guillain-Barré syndrome, particularly in sporadic cases, guiding treatment decisions. These studies may remain abnormal for weeks after illness onset, providing valuable information in later stages when botulinum toxin is likely undetectable. In public health emergencies requiring contingency or crisis care, the feasibility of conducting these studies may diminish. Therefore, when possible, electrodiagnostic testing should be considered to assist in diagnosing suspected botulism cases, as expert-conducted and interpreted EMG, RNS, and NCSs can yield useful diagnostic insights.

Pre-Operative Electrodiagnostic Studies for Prediction of Post-Operative Outcomes in Ulnar Neuropathy at the Elbow

In a systematic review, Meiling et al. (2023) examined the association between pre-operative EDX studies and post-operative pain and functional outcomes following ulnar nerve decompression and/or transposition for ulnar neuropathy at the elbow (UNE). Database search was carried out by an experienced librarian of all available studies in the English language from 1990 to June 8, 2022. Databases included Ovid Medline (R) and Epub Ahead of Print, In-Process & Other Non-Indexed Citations and Daily, Ovid Embase, Ovid Cochrane Central Register of Controlled Trials, and Scopus. Inclusion criteria consisted of RCTs, prospective and retrospective longitudinal studies, and studies involving adults 18 years of age or older who underwent ulnar nerve decompression and/or transposition for the treatment of UNE. Study quality and risk of bias were assessed using the National Heart, Lung, and Blood Institute (NHLBI) Study Quality of Assessment Tool. Certainty in evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. A meta-analysis was not performed. A total of 289 studies were screened, and 8 retrospective cohort studies met inclusion criteria comprising 762 patients. A decreased or absent pre-operative sensory nerve action potential amplitude (SNAP) showed significance with worse post-operative outcomes. The presence of pre-operative conduction block showed significance in higher quality studies. There was limited evidence for slow pre-operative motor conduction velocities or pre-operative EMG abnormalities and post-operative outcomes. Overall quality assessment indicated that 2 studies had "good", 4 "fair" and 2 "poor" quality of evidence. Certainty in evidence was "low" due to risk of bias. The authors concluded that a decreased or absent pre-operative ulnar SNAP may predict worse post-operative outcomes. Per higher quality studies, pre-operative conduction block at the elbow may also predict worse post-operative outcomes. These researchers stated that careful interpretation is needed with a full understanding of the limited evidence, risk of bias, and low certainty in evidence to support the use of pre-operative EDX to predict post-operative outcomes in UNE.

Appendix

Appendix A: AANEM Nerve Reference Values

For motor and sensory nerve reference values from the American Association of Neuromuscular & Electrodiagnostic Medicine, see AANEM Reference Values.

Source: AANEM, 2020

Appendix B: EDX Report

The following information should be included in the EDX report:

• Patient demographics
• Reason for referral
• Description of history and physical exam
• NCS examination reflects the following (preferably in a tabular (not narrative) format)
  
  
  • limb temperature (>32°C upper extremity, >30°C lower extremity)
  • type of study (sensory, motor, mixed)
  • side and nerve (e.g., left median)
  • stimulation and recording site (e.g., wrist, index)
  • SNAP/CMAP amplitude
  • distal peak or onset latency
  • conduction velocity
  • reference values
    
    

• EMG examination reflects the following (preferably in a tabular (not narrative) format)

  • side (left or right)
  • muscle tested
  • activity data (voluntary, insertional, spontaneous) Note: Needle EMG testing must include an evaluation at rest and voluntary activation
     
• Description of findings
• Probable diagnosis and location of pathology
• Study limitations and previous study information
• Signature with time stamp

Source: AANEM, 2011

Appendix C: Surface EMG, F-Waves, H-Reflex, and Blink Reflex Study Information

Surface electromyography (surface EMG or sEMG) is a noninvasive technique used to measure and record the electrical activity produced by skeletal muscles through sensors placed on the skin. Surface electrodes are usually employed for both stimulation and recording; whereas, needle electrodes may be used when there is a need to evaluate a nerve that is deep in the tissue, such as the sciatic nerve in the thigh, or the femoral nerve in an extremely obese individuals.

F-waves and H-reflex studies are performed to evaluate nerve conduction in portions of the nerve more proximal (near the spine) and, therefore, inaccessible to direct assessment using conventional techniques. Electrical stimulation is applied on the skin surface near a nerve site in a manner that sends impulses both proximally and distally. Characteristics of the response are assessed, including latency. Late responses provide information in the evaluation of radiculopathies, plexopathies, polyneuropathies (especially with multifocal conduction block or in suspected Guillain-Barré syndrome or chronic inflammatory demyelinating polyneuropathy), and proximal mononeuropathies. In some cases, they may be the only abnormal study.

Motor and sensory NCS studies and late responses (F-waves and H-reflex studies) are often complementary and performed during the same evaluation.

H-Reflex Studies

• Typically, only 2 H-reflex studies are performed in a given examination.
• H-reflex studies usually must be performed bilaterally because symmetry of responses is an important criterion for abnormality. When a bilateral H-reflex study is performed, the entire procedure must be repeated, increasing examiner time and effort; there are no economies of scale in multiple H-reflex testing.
• H-reflex studies usually involve assessment of the gastrocnemius/soleus muscle complex in the calf. Bilateral gastrocnemius/soleus H-reflex abnormalities are often early indications of spinal stenosis, or bilateral S1 radiculopathies.
• In rare instances, H-reflexes need to be tested in muscles other than the gastrocnemius/soleus muscle, e.g., in the upper limbs. In conditions such as cervical radiculopathies or brachial plexopathies, an H-reflex study can be performed in the arm (flexor carpi radialis muscle). Other muscles that may be tested, although rarely, are the intrinsic small muscles of the hand and foot.

F-Wave Studies

• Although the set-up for an F-wave study is similar to the set-up for a motor NCV study, the testing is carried out separately from motor NCV study, utilizing different machine settings and separate stimulation to obtain a larger number of responses (at least 10).
• The number of F-wave studies, which need to be performed on a given person, depends on the working diagnosis and the electrodiagnostic findings already in evidence. It may be appropriate in the same person to perform some motor NCV studies with an F-wave and others without an F-wave.

Blink Reflex

The blink reflex is an electrodiagnostic analog of the corneal reflex. The latency of the responses, including side-to-side differences, can help localize pathology in the region of the 5th or 7th cranial nerves, or in the brainstem. The latencies and amplitudes of directly elicited facial motor responses should be determined to exclude a peripheral abnormality if the blink reflexes are abnormal.

Appendix D: Coding Information for EMG performed with or without same day NCS

Note: EMG coding is based on the number of limbs examined (or, in certain cases, specific paraspinal muscle levels), but the choice of which group of CPT codes to use for billing depends on whether a NCS is also performed on the same day.

For EMG studies performed with a NCS on the same day, physicians should bill using CPT codes 95885 (limited study), 95886 (complete study), or 95887 (non-extremity study). These are considered “add-on” codes and may not be billed independent of a NCS code. These are billed in units based on the number of extremities tested. One unit includes all muscles tested in a particular extremity, with or without the relevant paraspinal muscles. A complete study of a limb should include at least 5 muscles that are innervated by 3 or more peripheral nerves (e.g., radial, ulnar, median, tibial, peroneal, femoral or 4 or more spinal levels. In some instances, a complete study may be billed without the relevant paraspinals muscles when this testing is contraindicated or not feasible and the reasons are documented. A non-extremity code can be billed when evaluating muscles innervated by the cranial nerves (e.g., laryngeal muscles, genioglossus), the phrenic nerve (i.e., diaphragm), paraspinal muscles assessed independent of limb testing, abdominal muscles, or other muscles not associated with an extremity. 

When NCS is not performed on the same day, physicians should bill using CPT codes 95860-95864 (compete studies, based on number of limbs evaluated), 95870 (limited study), 95865 (larynx), 95866 (hemidiaphragm), 95867 (unilateral muscles supplied by cranial nerves), 95868 (bilateral muscles supplied by cranial nerves), or 95869 (thoracic paraspinals). Only 1 unit of service of codes (95860-95864 may be reported per patient for a given examination.

Source: Adapted from Grierson et al. (2019)

Note: for codes performed without a NCS and not addressed in this policy, refer to the applicable CPB:

• CPT 95861 - CPB 0697 - Intraoperative Neurophysiological Monitoring
• CPT 95865 - CPB 0697 - Intraoperative Neurophysiological Monitoring
• CPT 95866 - CPB 0697 - Intraoperative Neurophysiological Monitoring
• CPT 95867 - 
  
  
  • CPB 0028 - Temporomandibular Disorders
  • CPB 0374 - Trigeminal Neuralgia: Treatments
  • CPB 0697 - Intraoperative Neurophysiological Monitoring
  • CPB 1039 - Venous Stenting for the Treatment of Idiopathic Intracranial Hypertension
    
    

• CPT 95868 - 

  • CPB 0028 - Temporomandibular Disorders
  • CPB 0697 - Intraoperative Neurophysiological Monitoring
  • CPB 1039 - Venous Stenting for the Treatment of Idiopathic Intracranial Hypertension
    
    
• CPT 95869 - CPB 0697 - Intraoperative Neurophysiological Monitoring
• CPT 95870 - CPB 0697 - Intraoperative Neurophysiological Monitoring
• CPT 95873, 95874 - 
  
  
  • CPB 0016 - Back Pain - Invasive Procedures
  • CPB 0113 - Botulinum Toxin
  • CPB 0253 - Vocal Cord Paralysis / Insufficiency Treatments
  • CPB 0725 - Post-Herpetic Neuralgia
  • CPB 0745 - Facial Nerve Paralysis
    
    

• CPT 51784 - CPB 0223 - Urinary Incontinence

  Note: for NCS codes performed without an EMG and not addressed in this policy refer to the applicable CPB:

• CPT 95907 - CPB 0697 - Intraoperative Neurophysiological Monitoring

References